Solvent bleaching process

ABSTRACT

Cotton and other cellulosic fibers are effectively and rapidly bleached by wetting with a suspension of hydrogen peroxide in a chlorinated hydrocarbon solvent and drying the wetted material by exposure to hot chlorinated hydrocarbon solvent vapor. The process is particularly effective with raw cotton and cotton linters.

dDd-lUn United States Patent 11 1 Cunningham et a1.

SOLVENT BLEACHING PROCESS inventors: William K. Cunningham, Midland,

Mich.; Donald B. Knight, Greenville,

Assignee: The Dow Chemical Company,

Midland, Mich.

Filed: June 7, 1972 Appl. No.: 260,599

U.S.Cl ..8/l1l,8/10l,8/142,

252/104, 252/162, 252/170, 252/171 Int. Cl. D061 3/02, D061 3/06 Field of Search 8/111, 101, 142;

Oct. 2, 1973 [56] References Cited UNITED STATES PATENTS 3,635,667 1/1972 Keay et a1 8/111 X 3,708,260 1/1973 Marshall et a1. 8/111 Primary Examiner-Mayer Weinblatt Att0rneyWilliam M. Yates et al.

[57] ABSTRACT 9 Claims, No Drawings SOLVENT BLEACI-IING PROCESS BACKGROUND OF THE INVENTION The present invention relates to an improved process for bleaching cellulosic fibers with a peroxide composition. It relates particularly to a process whereby rapid bleaching of cellulosic fibers is obtained by use of aqueous peroxide in combination with a chlorinated hydrocarbon solvent.

Cotton and other cellulosic textile fibers and fabrics have been bleached in the past with aqueous solutions of peroxide, usually hydrogen peroxide. Although effective bleaching was obtained, this kind of process typically required immersion of the material in a boiling peroxide solution for periods of time up to several hours. In recent years, a more rapid bleaching and desizing process has been developed wherein a suspension of aqueous hydrogen peroxide in trichloroethylene or other such chlorinated solvent is applied to the textile material and the wetted material is then steamed to remove the solvent, see, for example, Gennan Offenleg. Pat. No. 2,022,929. The treated material is then subjected to aqueous washing and rinsing and finally it is dried. Although the bleaching action thereby provided is relatively rapid, only partial bleaching is obtained and the subsequent washing, rinsing, and drying steps which are required make the entire process a rather lengthy one.

SUMMARY OF THE INVENTION It has now been found that cotton and other cellulosic textile fibers are rapidly and efficiently bleached by wetting with a suspension or emulsion of aqueous peroxide, in a chlorinated lower aliphatic hydrocarbon solvent and then contacting the wetted fibers with superheated chlorinated solvent vapor until the fibers are essentially dry. The concentration of the peroxide, in its aqueous solution, can vary between about and 60 weight percent. Preferably, the solvent in the peroxide suspension and the vaporized solvent are the same. The

DETAILED DESCRIPTION The preferred bleaching component in the present process is hydrogen peroxide which is ordinarily supplied in the form of one of its commercially available aqueous solutions. Other peroxygen compounds which can be used in the present process are hydroperoxides, peroxyacids and their salts and other peroxides. Examples of these include tert-butyl hydroperoxide, peracetic acid, sodium perborate, and sodium peroxide.

The concentration of aqueous hydrogen peroxide can vary from about 10 percent to about 60 percent by weight and a concentration of about 10-50 percent is preferred. Equivalent concentrations of other peroxy compounds can be used. The total amount of peroxide in the system can vary from about 0.05 percent to about 15 percent, preferably to about 5 percent, based on the weight of fiber. The same limits apply to the water.

Any of the commonly used chlorinated lower aliphatic hydrocarbon solvents can be used in the process,

, for example, carbon tetrachloride, methylene chloride,

ethylene dichloride, propylene dichloride, methyl chlo roform, trichloroethylene and perchloroethylene or mixtures thereof. Trichloroethylene and especially perchloroethylene are preferred.

The temperature of the solvent-aqueous peroxide mixture used to wet the unbleached fiber by immersion, spraying, or padding is suitably about room temperature or moderately above that. Some advantage is obtained if the fiber is dried before this step. The critical solvent vapor drying step which follows is effective at a temperature above the normal boiling point of the liquid solvent in the approximate range of 65-l45 C. At lower temperatures, only partial bleaching is obtained while scorching of the fibers when fully dried is likely above about l45 C. The drying process is best carried out at about l22-l 40 C. for the preferred perchloroethylene. Somewhat higher vapor temperatures can be used briefly if the fiber or fabric is only partially dried, for example, up to C.

Both the temperature and the solvent vapor atmosphere are necessary to obtain the improved bleaching provided by this invention. When the fibers or fabric wetted with the solvent-peroxide mixture is dried at about room temperature in any atmosphere, little or no bleaching is obtained. Drying in hot air or in steam as in prior art processes provides only partial bleaching as compared to the results of this process, see Keay et al., US. Pat. No. 3,635,667.

The solvent-aqueous peroxide mixture is preferably in the form of an emulsion or suspension maintained by the presence of a small quantity of surface active agent, usually in the range of about 001-] percent based on the liquid weight. Any surface active agent capable of creating a water-in-chlorinated solvent suspension is operable and anionic, nonionic, and cationic materials can be used. The surface active agent can be any of the commonly used textile or dry cleaning wetting agents which are soluble at least to the extent of 0.01 percent in chlorinated hydrocarbon solvents. Representative materials are petroleum sulfonates, the diethanolamide of lauric acid, polyethylene oxide adducts of long chain alcohols or alkylphenols, either as the nonionic adducts or as phosphate esters of these, dioctyl sodium sulfosuccinate, and other such compounds. All are effective in the process although practical considerations restrict the choice to compounds that do not discolor the textile material or leave an objectionable residual odor on it, that are not destroyed by the peroxide present, and that are not skin sensitizers. The presence of a surface active agent is not critical to operability of the bleaching process, but it is preferred particularly for the rapid fiber wettability and greater absorbency thereby obtained.

The aqueous phase in the system is preferably neutral or moderately basic, for example, about pH 7-11. The pH level can be adjusted as desired by addition of small amounts of base or buffering compound such as sodium hydroxide, sodium oxalate, sodium silicate, sodium bicarbonate or ammonia.

This process is particularly effective and valuable in bleaching raw cotton and cotton linters in which application it provides fast and effective treatment. It is also applicable to bleaching of cellulosic fibers and fabrics generally, for example, cotton in polyester blends, linen, ramie, and other fibers of plant origin. The process can also be applied as an adjunct to or substitute for conventional dry cleaning of white goods. Additives such as optical brighteners, antiredeposition agents, and the like can also be present in the system.

Examples l-ll Four inch squares of unbleached cotton greige were added to the test perchloroethylene composition in a stainless steel cup and the contents of the cup were stirred at the desired temperature for 2 minutes. The test squares were then removed from the cup, drained briefly and dried, two being dried in air at ambient temperature and two being dried by perchloroethylene vapor at l2ll43 C. for 5 minutes. The reflectance of the swatches before treatment and after drying was measured using a Photovolt photometer equipped with TABLE 2 Example H:

Wt. percent on Fabric Reflectance Water Detergent Drying Green Blue whiteness 0.l 0.23 0.1 Air 80 66 40 Vapor 78 70 34 0.2 L0 0.] Air 80 72 48 Vapor 83 76 55 0.2 0.45 0.2 Air 77 67 37 Vapor 78 66 Further bleaching tests were run on squares of unbleached cotton as described in Examples l-ll except that the temperature and method of drying and the detergent were varied as well as the concentration and amount of aqueous hydrogen peroxide. Pairs of treated swatches were dried in a circulating air oven and in hot perchloroethylene vapors in each case and in some cases, pairs of swatches were also dried in air at room temperature. Examples 12-14 and 18-20 were run with aqueous peroxide at pH 7 using 0.l percent sodium pe'- troleum sulfonate based on the solvent weight whereas Wt. percent on fabric Reflectance Example H1O: Water Detergent Drying Green Blue whiteness Control..... (Unbleached cotton) 73 56 5 Control..... 0 0 0.5 Air 72 58 I6 Vapor 75 61 l9 Control..... 0 0.45 0.5 Air 71 60 27 Vapor 75 64 3l 1 0.05 0.23 0.5 Air 77 65 29 Vapor 80 70 2 0.05 L0 0.5 Air 76 65 32 Vapor 8| 72 3 0.2 0.45 0.5 Air 79 69 29 Vapor 83 76 4 0.5 L25 0.5 Air 79 70 43 Vapor 84 79 64 5 0.2 0.45 0.l Air 78 67 34 Vapor 84 78 6 0.2 0.45" 0.l Air 71 29 Vapor 85 8l 6) 7 0.2 2.0 0.] Air 76 64 28 Vapor 84 78 60 8 0. 5.0 0.l Air 75 64 31 Vapor 83 55 whiteness (4 x Blue)-(3 x Green) pH l0 Examples -17 were run at pH 10 using 0.5 percent of a nonionic detergent, the nonylphenol adduct of four moles of ethylene oxide. These data are listed in Table 3.

ture is about -l45 C.

3. The process of claim 1 wherein the fiber material is cotton.

4. The process of claim 3 wherein the peroxide is hy- TABLE 3 Wt. percent on Fabric Reflectance Example H 0 Water Drying Green Blue Control (Unbleached Cotton) 71 56 Control 0 0 Oven or hot solvent 61 vapor 12 0.01 0.02 Oven. l 10- 1 15 C. 78 66 Vapor. 115 C. 70 13 0.02 0.04 Oven. -115C. 80 69 Vapor, l 15 C. 83 74 14 0.08 0.16 Oven, 1 10- l 15C. 80 70 Vapor. C. 84 75 15 0.01 0.02 Oven. l l0- l 15C. 76 67 Vapor, C. 78 69 16 0.02 0.04 Oven. 110- 1 15 C. 79 70 Vapor. 120 C. 81 73 17 0.08 0.16 Oven,ll0ll5C. 81 76 Vapor. 120 C. 85 82 18 0.02 0.08 Air, room temp. 74 59 Oven.l10ll5C. 78 66 Vapor. C. 81 71 19 0.04 0.16 Air. room temp. 75 62 Oven.1l0-115C. 79 70 Vapor. 140 C. 82 74 20 0.08 0.32 Air, room temp. 76 63 Oven.l10-115C. 80 71 Vapor. 140C. 84 77 ln substantially the same way as shown in the above examples, cotton in polyester blends, linen, ramie, and other vegetable fibers generally which are primarily cellulosic in nature are efi'ectively bleached by this process.

We claim:

1. A process for bleaching a cellulosic fiber material which comprises wetting the material with a mixture of aqueous peroxide and chlorinated lower hydrocarbon solvent, the concentration of said peroxide calculated on the basis of hydrogen peroxide equivalent being about 10-60 percent based on the weight of aqueous solution, and contacting the wetted material with superheated chlorinated lower hydrocarbon solvent vapor until the material is essentially dry.

2. The process of claim 1 wherein the vapor temperadrogen peroxide.

5. The process of claim 4 wherein the vaporized solvent and the solvent of the peroxide composition are the same.

6. The process of claim 5 wherein the solvent is perchloroethylene.

7. The process of claim 6 wherein the temperature is 122-l40 C.

8. The process of claim 1 wherein the aqueous peroxide-solvent mixture contains about 0.01-1 percent based on the weight of mixture of a surface active agent capable of converting said mixture into a stable suspension.

9. The process of claim 1 wherein the aqueous solution has a pH of about 7-11.

t i t t i 

2. The process of claim 1 wherein the vapor temperature is about 65*-145* C.
 3. The process of claim 1 wherein the fiber material is cotton.
 4. The process of claim 3 wherein the peroxide is hydrogen peroxide.
 5. The process of claim 4 wherein the vaporized solvent and the solvent of the peroxide composition are the same.
 6. The process of claim 5 wherein the solvent is perchloroethylene.
 7. The process of claim 6 wherein the temperature is 122*-140* C.
 8. The process of claim 1 wherein the aqueous peroxide-solvent mixture contains about 0.01-1 percent based on the weight of mixture of a surface active agent capable of converting said mixture into a stable suspension.
 9. The process of claim 1 wherein the aqueous solution has a pH of about 7-11. 